JZ49 把字符串转换成整数

本文最后更新于：2022年4月9日 中午

image-20211010151104044

Solution

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class Solution {
public:
    int StrToInt(string str) {
        int len = str.size();
        if (len == 0) return 0;
        long res = 0, flag = 1;
        int i = 0;
        while (str[i] == ' ') {
            i++;
            if (i >= len) return 0;
        }
        if (str[i] == '-' || str[i] == '+') {
            if (str[i] == '-') flag = -1;
            i++;
        }
        for (i; i < len; ++i) {
            if (str[i] < '0' || str[i] > '9') return 0;
            res = res * 10 + (str[i] - '0');
            if (res >= INT_MAX && flag == 1) return INT_MAX;
            if (res > INT_MAX && flag == -1) return INT_MIN;
        }
        return res * flag;
    }
};